Interpretive Summary: Hamsters fed a high fat diet supplemented with hydrolysate of proteins extracted from brown rice gained less weight than control animals. Liver cholesterol was lower and fecal bile acid excretion was higher. Fat metabolism was changed to less storage and more fat burning in the hamsters fed brown rice protein hydrolysate.

Technical Abstract:
The physiological effects of the hydrolysates from white rice, brown rice, and soy isolate were compared to the original protein source. White rice, brown rice, and soy protein were hydrolyzed with the food grade enzyme, alcalase2.4 L®. Male Syrian hamsters were fed high-fat diets containing either 20% casein (control) or 20% extracted proteins or their hydrolysates as the protein source for three weeks. The brown rice protein hydrolysate (BRPH) diet group reduced weight gain 76% compared with the control. BRPH fed animals also had lower final body weight, liver weight, very low density lipoprotein cholesterol, liver cholesterol and higher fecal fat and bile acid excretion than the control. Feed intake was not different between diet treatments. Expression levels of hepatic genes for lipid oxidation, PPAR a, ACOX1, CPT1 were highest for hamsters fed the BRPH supplemented diet. Expression of CYP7A1, the gene regulating bile acid synthesis, was higher for all rice and soy diets. Expression of CYP51, a gene coding for an enzyme involved in cholesterol synthesis, was highest in the BRPH diet group. The results suggest that the alcalase hydrolysis of brown rice protein results in unique peptides that reduce weight gain and hepatic cholesterol synthesis.